Question

In class I mentioned that we used to show an actual ballistic pendulum where a rifle is shot into a heavy block to see how the block moves. Assume a 4.7 gram bullet is fired at 678 m/s into a 4.8 kg block of wood. The block hangs from a long string to approximate 1D motion. How fast does the block move just after the collision in m/s?

Answer 1

Answer:

0.66 m/s

Explanation:

This is an inelastic collision, for that reason the conservation of momentum law allows us to determine the final velocity of both, the bullet and block together after the collision:

$m_{bullet} v_{bullet0} +m_{block} v_{block} =(m_{bullet}+m_{block})v_{f} \\v_{f} =\frac{m_{bullet} v_{bullet0} }{m_{bullet}+m_{block}} \\v_{f} =\frac{0.0047kg*678m/s}{4.8kg+0.0047kg}\\v_{f} =0.66 m/s$